1. Field of the Invention
The present invention relates to an X-ray spectroscopic analyzing apparatus having a source of X-rays for radiation onto a sample to be analyzed.
2. Description of the Prior Art
As an apparatus for achieving an elemental analysis of a sample to be analyzed, a fluorescent X-ray analyzing apparatus has been known which comprises a source of X-rays, for example, an X-ray tube, for radiating an excitation X-ray beam towards a sample to be analyzed, and a fluorescent X-ray detector for detecting the intensity of fluorescent X-rays coming from the sample to determine elements contained in the sample, In this type of fluorescent X-ray analyzing apparatus, a low-order beam having a relatively high intensity is spectroscopically selected from a spectrum of the X-rays emitted from the X-ray tube and is used as the excitation X-rays.
With the prior art fluorescent X-ray analyzing apparatus, it has been found that no element of the sample having a wavelength component lower than that of the low-order beam cannot be spectroscopically determined. Accordingly, where the sample contains the same element as that contained in a target material of the X-ray tube, the spectroscopic determination of such element is not possible.
By way of example, if the target material is made of tungsten (W), and so long as a WL.beta..sub.1 beam (.lambda.=1.2818 .ANG., E=9.671 keV) having a relatively high intensity is employed for the excitation X-ray beam, the determination of the presence of tungsten in the sample is not possible even though the sample in fact contain tungsten. This is because the wavelength at the absorption edge peculiar to tungsten is shorter than the wavelength of the WL.beta..sub.1 beam.
This is also true of other elements than tungsten. By way of example, arsenic cannot be spectroscopically analyzed with the prior art fluorescent X-ray analyzing apparatus because the wavelength (.lambda.=1.045 .ANG.) at the absorption edge peculiar to arsenic is shorter than the wavelength of the WL.beta..sub.1 beam.
Apart from the foregoing prior art, a total reflection fluorescent X-ray analyzing method is also well known in which a primary X-ray beam is radiated so as to be incident upon a sample to be analyzed at a minute angle of incidence so that fluorescent X-rays reflected from a surface region of the sample can be analyzed for the elemental determination. In the practice of this prior art fluorescent X-ray spectroscopic analyzing method utilizing the total reflection, a monochromatic light is employed for the primary X-ray beam. However, where the monochromatic light is employed, it has often been observed that the spectroscopic analysis tends to result in a measurement error depending on preset values of parameters used during the analysis.